Sajid Javid today launched a broadside at Boris Johnson in the Commons, saying the Prime Minister must listen with “respect” to ministers and not saddle future generations with debts for his spending ambitions.

The former chancellor called for “mutual respect and trust” within the Government and blamed the PM’s adviser Dominic Cummings for a breakdown that had jeopardised the “national interest”.

Saying that Mr Johnson must let ministers “speak truth to power”, he then opened up the faultline running through the Conservative Party over spending, borrowing and taxes — and demanded that the Treasury should be heeded properly as guardian of the public purse.

After the speech, Mr Johnson stood up unexpectedly with an olive branch – praising Mr Javid’s “immense service” and saying he had “friends and admirers on all sides”.

The drama unfolded after Prime Minister’s Questions when Mr Javid stood up for his first speech from the backbenches in eight years.

He made clear he will not quit the political frontline, saying “I do not intend this to be my last chapter in public life, in whatever form that takes.”

He expressed no personal bitterness, shrugging off his return to the backbenches as “the circle of life”.

In an apparent jibe at the Prime Minister, he said: “It’s fair to say that not everyone in the centre of government feels the pressure to balance the books.”

He went on: “At a time when we need to do much more to level up across the generations, it would not be right to pass the bill for our day to day consumption to our children and grandchildren.”

He warned against the Prime Minister’s style of government, including the role played by maverick adviser Dominic Cummings.

Mr Javid blamed the PM’s adviser Dominic Cummings for a breakdown that had jeopardised the “national interest” (Getty Images)

“Conservatives especially believe that no particular person — or even government — has a monopoly on the best ideas,” he said, apparently referring to both Mr Johnson’s attempts to gather power at No 10 and his reliance on the advice of the powerful Mr Cummings.

“It is through the checks and balances of credible institutions, be it the Treasury, the Bank of England, the Office of Budget Responsibility, or indeed this House, that we arrive at sensible decisions in the national interest.”

Urging the PM to listen to a range of voices, he said: “There is no one size that fits.”

But he warned that success also depended on “the personalities involved just as much as the processes”.

“It depends on the mutual respect and trust that allows for constructive, creative tension between their teams.”

Then the former Chancellor turned to the day of his shock resignation during the reshuffle on February 13 when he was given an ultimatum to sack his four political advisers.

“It has always been the case that advisers advise, ministers decide —– and ministers decide on their advisers,” he said, defending the right of ministers to pick their teams.

“I couldn’t see why the Treasury — with the vital role that it plays — should be the exception to that.”

He continued by saying a Prime Minister must listen to ministers, especially the Chancellor who was the only minister responsible for balancing the books.

“A Chancellor, like all Cabinet Ministers, has to be able to give candid advice to a Prime Minister — to speak truth to power,” he said.

“I believed that the arrangement proposed would significantly inhibit that — it would not have been in the national interest.

Mr Johnson during a Cabinet meeting one day after the reshuffle (AP)

“So while I was grateful for the continued trust of the Prime Minister in wanting to reappoint me, I’m afraid they were conditions I could not accept in good conscience.”

Mr Javid went on: “Now I don’t intend to dwell further on the details and personalities. The comings and goings, if you will.” His pun on Cummings pointed directly at the PM’s chief adviser.

He then appealed: “I very much hope the new Chancellor will be given the space to do his job without fear or favour.”

Mr Javid turned to perhaps the most powerful section of his speech, on the public finances and the key role of the Treasury in preventing overspending.

He warned: “The Treasury must also be allowed to play its role as a finance ministry with the strength and credibility that requires.”

Mr Javid said: “Already, our tax burden is the highest in 50 years.”

He said the fiscal rules he had written into the Tory manifesto were “critical” and they “set in stone” the importance of keeping debt lower at the end of the Parliament than at the beginning.

But he concluded by saying he could “look to the future not with apprehension, but with great optimism”.

“This is a shared vision, and I firmly believe that the Prime Minister has the tenacity, the energy and the skill to see it through. “I want to leave the House in no doubt that he has my confidence.”

The speech will establish Mr Javid as the pre-eminent voice on the backbenches expressing caution about Mr Johnson’s spending ambitions.

Mr Javid’s allies emphasised it was “constructive and positive” and not intended to damage the Government. However, personal statements have often had a bigger impact that their authors intended.

The most famous was Lord Howe’s in 1990 with the cutting line that ministers sent to Europe felt like batsmen who discovered “the moment the first balls are bowled, that their bats have been broken before the game by the team captain”.

Another former Chancellor, Lord Lamont, defenestrated John Major’s leadership with the charge that his government was “in office, but not in power”. The pair reputedly never spoke again.

Robin Cook’s resignation on the eve of the Iraq invasion in 2003 saw him give an electrifying and forensic analysis of weaknesses in Tony Blair’s case for war to topple Saddam Hussein, which earned a rare round of applause.

Boris Johnson’s statement after quitting as Foreign Secretary in 2018 saw him accuse Theresa May of having “dithered” and “burned through negotiating capital” over Brexit. He also set out his rival vision, setting in train his own leadership bid.

With successor Rishi Sunak’s Budget a fortnight away, Mr Javid’s warning about public finances will be seen as significant. He fought hard during the general election to have fiscal rules in the manifesto to curb borrowing for current spending.

Today the respected Institute for Fiscal Studies pointed out that if the Prime Minister drives up overall spending without raising revenues, the fiscal rules will be the shortest-lived in history